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Andre Richter 2019-10-21 22:08:43 +02:00 committed by Andre Richter
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06_drivers_gpio_uart/README.md
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@ -6,6 +6,13 @@ Now that we enabled safe globals in the previous tutorial, the infrastructure is
laid for adding the first real device drivers. We throw out the magic QEMU laid for adding the first real device drivers. We throw out the magic QEMU
console and use a real UART now. Like serious embedded hackers do! console and use a real UART now. Like serious embedded hackers do!
- For the first time, we will be able to run the code on the real hardware.
- Therefore, building is now differentiated between the **RPi 3** and the **RPi4**.
- By default, all `Makefile` targets will build for the **RPi 3**.
- In order to build for the the **RPi4**, prepend `BSP=rpi4` to each target. For example:
- `BSP=rpi4 make`
- `BSP=rpi4 make doc`
- Unfortunately, QEMU does not yet support the **RPi4**, so `BSP=rpi4 make qemu` won't work.
- A `DeviceDriver` trait is added for abstracting `BSP` driver implementations - A `DeviceDriver` trait is added for abstracting `BSP` driver implementations
from kernel code. from kernel code.
- Drivers are stored in `bsp/driver`, and can be reused between `BSP`s. - Drivers are stored in `bsp/driver`, and can be reused between `BSP`s.
@ -18,19 +25,54 @@ console and use a real UART now. Like serious embedded hackers do!
## Boot it from SD card ## Boot it from SD card
Some steps for preparing the SD card differ between RPi3 and RPi4, so be careful.
### Common for both
1. Make a single `FAT32` partition named `boot`. 1. Make a single `FAT32` partition named `boot`.
2. Copy [bootcode.bin](https://github.com/raspberrypi/firmware/raw/master/boot/bootcode.bin), [fixup.dat](https://github.com/raspberrypi/firmware/raw/master/boot/fixup.dat) and [start.elf](https://github.com/raspberrypi/firmware/raw/master/boot/start.elf) from the [Raspberry Pi firmware repo](https://github.com/raspberrypi/firmware/tree/master/boot) onto the SD card. 2. On the card, generate a file named `config.txt` with the following contents:
3. Copy our [kernel8.img](kernel8.img) onto the SD card.
4. Insert the SD card into the RPi and connect the USB serial to your host PC. ```txt
init_uart_clock=48000000
```
### Pi 3
3. Copy the following files from the [Raspberry Pi firmware repo](https://github.com/raspberrypi/firmware/tree/master/boot) onto the SD card:
- [bootcode.bin](https://github.com/raspberrypi/firmware/raw/master/boot/bootcode.bin)
- [fixup.dat](https://github.com/raspberrypi/firmware/raw/master/boot/fixup.dat)
- [start.elf](https://github.com/raspberrypi/firmware/raw/master/boot/start.elf)
4. Run `make` and copy the [kernel8.img](kernel8.img) onto the SD card.
### Pi 4
3. Copy the following files from the [Raspberry Pi firmware repo](https://github.com/raspberrypi/firmware/tree/master/boot) onto the SD card:
- [fixup4.dat](https://github.com/raspberrypi/firmware/raw/master/boot/fixup4.dat)
- [start4.elf](https://github.com/raspberrypi/firmware/raw/master/boot/start.elf)
- [bcm2711-rpi-4-b.dtb](https://github.com/raspberrypi/firmware/raw/master/boot/bcm2711-rpi-4-b.dtb)
4. Run `BSP=rpi4 make` and copy the [kernel8.img](kernel8.img) onto the SD card.
### Common again
5. Insert the SD card into the RPi and connect the USB serial to your host PC.
- Wiring diagram at [top-level README](../README.md#usb-serial). - Wiring diagram at [top-level README](../README.md#usb-serial).
5. Run `screen` (you might need to install it first): 6. Run `screen` (you might need to install it first):
```console ```console
sudo screen /dev/ttyUSB0 115200 sudo screen /dev/ttyUSB0 115200
``` ```
6. Hit <kbd>Enter</kbd> to kick off the kernel boot process. 7. Hit <kbd>Enter</kbd> to kick off the kernel boot process. Observe the output:
7. Exit screen by pressing <kbd>ctrl-a</kbd> <kbd>ctrl-d</kbd> or disconnecting the USB serial.
```console
[0] Booting on: Raspberry Pi 3
[1] Drivers loaded:
1. GPIO
2. PL011Uart
[2] Chars written: 84
[3] Echoing input now
```
8. Exit screen by pressing <kbd>ctrl-a</kbd> <kbd>ctrl-d</kbd> or disconnecting the USB serial.
## Diff to previous ## Diff to previous
```diff ```diff
@ -483,7 +525,8 @@ diff -uNr 05_safe_globals/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs 06_drivers_gp
+ // Convert newline to carrige return + newline. + // Convert newline to carrige return + newline.
+ if c == ' + if c == '
' { ' {
+ self.write_char(' ') + self.write_char('
')
+ } + }
+ +
+ self.write_char(c); + self.write_char(c);
@ -583,7 +626,8 @@ diff -uNr 05_safe_globals/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs 06_drivers_gp
+ let mut ret = inner.DR.get() as u8 as char; + let mut ret = inner.DR.get() as u8 as char;
+ +
+ // Convert carrige return to newline. + // Convert carrige return to newline.
+ if ret == ' ' { + if ret == '
' {
+ ret = ' + ret = '
' '
+ } + }
@ -707,7 +751,8 @@ diff -uNr 05_safe_globals/src/bsp/rpi.rs 06_drivers_gpio_uart/src/bsp/rpi.rs
- // Convert newline to carrige return + newline. - // Convert newline to carrige return + newline.
- if c == ' - if c == '
' { ' {
- self.write_char(' ') - self.write_char('
')
- } - }
- -
- self.write_char(c); - self.write_char(c);